1. Field of the Invention
The present invention relates to abdominal impedance measurement apparatuses and body composition determination apparatuses for human bodies.
2. Description of Prior Art
For correctly taking measurements of areas of visceral fat and subcutaneous fat in the bodies of humans, body fat determination apparatuses have been used which calculates body fat data on the basis of tomographic images obtained by various CT (computed tomography) procedures, including X-ray CT and impedance CT, or by MRI (magnetic resonance imaging).
Conventionally, studies have been made in which indexes of body fat were calculated on the basis of impedances measured using impedance measuring electrodes that may be brought into contact with the abdomen of a human subject. For example, according to one study, the mass or area of visceral fat of a human body is calculated on the basis of an impedance measured using a pair of current-supplying electrodes in contact with the anterior and posterior surfaces of the abdomen and voltage-measurement electrodes in contact with flanks of the abdomen, and by the waist circumference. The calculation method is obtained by correlation among the results of CT, the impedance, and the waist circumference, as disclosed in Miwa RYO, Development of Visceral-fat Measuring Method Using Abdominal Bioelectrical Impedance, Himan Kenkyu (Journal of Japan Society for the Study of Obesity), Japan, Japan Society for the Study of Obesity, 2003, Vol. 9, No. 2, pp. 32-38.
There has also been a study in which impedance measurement electrodes are mounted on a belt that is wound around the abdomen of a human subject, whereby the impedance measurement electrodes are brought into contact with the anterior surface of the abdomen, and the subcutaneous fat mass is estimated from the measured abdominal impedance, as disclosed in Hermann SCHARFETTER and five others, Assessing abdominal fatness with local bioimpedance analysis: Basics and experimental findings), [online], [Found in a search performed on Feb. 15, 2007], Internet URL: http://www.imt.tugraz.at/scharfetter/no_sync/publications/scharfetter_IJO—01.pdf#search=‘hermann%20scharfetter%20assessing%20abdominal’ and in JP-A-11-113870.
In the measurement of bioimpedance in humans, even for the same human subject, the measured results may vary depending on the positions of the measurement electrodes. Therefore, in order to ensure the reproducibility of measurements, the measurement electrodes should always be placed at the same locations. For example, it is possible to consider the transverse plane that passes through the navel of a human subject and is vertical to the median line to be the reference plane relative to which measurement electrodes should always be arranged.
However, it is difficult, in practice, to arrange impedance measurement electrodes at such reference positions. For example, in the method in which a belt on which impedance measurement electrodes are arranged is wound around the abdomen, there is the possibility that the positions of the measurement electrodes may be out of alignment by deformation of the belt. Furthermore, when the belt is wound around the abdomen, the reference positions cannot be definitely confirmed in most instances because the reference positions cannot be seen by the human subject or by anyone else due to the belt.